As disclosed in the above patents, in web handling processes wherein a web of flexible material such as a fabric, paper, or metal, is continuously passed at high speeds partly around a guide roll either fixed or rotatably supported on a shaft, it is known to support one or both ends of the shaft by a device capable of measuring the transverse or radial forces exerted on the roll by the tensions in the moving web and then making continuing adjustments to the web tension, responsive to the ongoing web tension measurements, either by manual or automatic control equipment. These known web tension measuring devices are customarily comprised of a sensor in the form of a strain beam cantilever mounted on a fixed frame and the flexurable free end of which is coupled to and supports an end of the guide roll shaft through either a thin flexurable steel diaphragm or a pivotal connection such as a self-aligning bearing. Strain gauges attached to the strain beam and connected in an electrical circuit then generate a continuing electrical signal representative of the beam deflection by the web tension forces and thus representative of the instantaneous tension in the moving web.
While the use of a flexurable diaphragm to support the end of the guide roll shaft of such web tension measuring devices is advantageous for a number of reasons such as avoiding the introduction of hysteresis into the measurements of the beam deflection and permitting minor amounts of shaft misalignment and length expansion to occur without seriously affecting the accuracy of such measurements, the diaphragm nevertheless is limited in the amount of tolerance which it has for such variables. In addition, the life of the diaphragm is somewhat limited because of the constant flexing thereof during use which leads to fatigue and failure of the diaphragm in a relatively short period of operating time, thus necessitating the disassembly and reassembly of the apparatus from time to time to enable replacement of the damaged diaphragm. To avoid such difficulties, therefore, web tension measuring devices of the general type referred to above and commonly in use at present generally have been provided with sliding or ball type pivoting connections instead of a flexurable diaphragm for coupling the end of the guide roll shaft to and supporting it on the flexurable end of the cantilever mounted strain beam of the device.
Prior known types of web tension measuring devices employing such sliding or ball type pivotal or self-aligning bearings for connecting the end of the guide roll support shaft to the unsupported free end of the flexurable strain beam have not proven entirely satisfactory for one reason or another, however, for every form of service application. Included among these various reasons for their not being entirely satisfactory in all cases are their susceptibility to unacceptably high hysteresis, the critical and expensive manufacturing procedures involved in their fabrication, the lack of any provision for self-lubrication of the self-aligning bearing to prolong the service life thereof and minimize hysteresis, the limited ability of the ball bearing type shaft supports to accommodate shaft expansion, their involved assembly and disassembly procedures, and the many component parts of which some of these prior known devices are constituted.